Variable view arthroscope

ABSTRACT

A variable-view arthroscope or similar instrument (endoscope, etc.) includes a housing tube with an object input end. The housing tube contains an object input assembly and a portion of a light relay assembly. The object input assembly includes an input lens and a first mirror. In some embodiments, the object input assembly includes a second mirror, and in alternative embodiments, the object input assembly includes a prism. The object input assembly passes images received from a viewing area to an object relay assembly that transmits the image object to the control end of the arthroscope. In some embodiments, the light relay assembly is formed of two mirrored rods. A control varies the position of the object input assembly to change the a viewing position of the arthroscope. In some embodiments, the control includes a push rod driven by a slide and cam/axle assembly.

FIELD OF THE INVENTION

The invention relates generally to arthroscopes, endoscopes and similaroptical instruments and more specifically to variable view arthroscopes.

BACKGROUND OF THE INVENTION

Arthroscopes and similaroptical instruments, such as endoscopes, areused in medical applications, such as suirgery and examination, as wellas in non-medical applications that similarly involve visual inspectionof a confined or inaccessible space that constitutes the working area.Although the present invention is described here with reference to anarthroscope or similar instrument employed for surgery, the inventionmay be useful for other applications and is intended to embrace allsuitable variations.

Over the last fifteen or more years, minimally invasive surgery hasbecome a mainstream surgical technique. Within the orthopedic field, inparticular, arthroscopy and similar techniques that employ devices suchas arthroscopes have become the most common surgical procedures.Minimally invasive surgery is less painful for the patient and, in mostinstances, can be performed more quickly and safely than surgery thatrequires greater invasion of the patient's body; other benefits ofminimally invasive surgery include that administration of anesthesia issimpler for minimally invasive surgery, that patients heal more quickly,that hospital stays may be reduced in length or even eliminated, andthat the procedures are more cost effective.

The value of using minimally invasive surgical techniques may be limitedby the capabilities of the arthroscopes, endoscopes and other principaloptical instruments employed. In particular, the rather limited field ofview afforded by even the best available instruments that satisfy thedimensional and other requirement of surgical applications has limitedthe useful scope of minimally invasive surgical techniques. Typically,the larger the field of view, the greater the usefulness of theinstrument for most applications.

Several methods for widening the field of view offered byarthroscopic/endoscopic instruments have been proposed, but they havenot been especially successful. Generally, such proposals have requiredpacking a plurality of movable lenses or prisms into the input end ofthe instrument; the resulting problems of precision of construction,precision of relative movements, space requirements, opticaldistortions, and elimination of undesired ambient light have beensubstantial.

Illuminating the viewing area to obtain a usable image is anotherrequirement of arthroscopes and similar instruments. Without adequatelight, the resultant image does not contain sufficient information to bemaximally useful. Light is typically provided to the object input end ofthe arthroscope from an external source through a light guide. The lightfrom the external source is transferred to an internal light guide inthe arthroscope at one end of the arthroscope and transmitted to thedistal end of the arthroscope via the internal light guide, where thelight generally diffuses to light the viewing area around the distal endof the arthroscope. The external source typically includes a lightconnected to a fiber optic bundle; the external fiber optic bundle ismechanically coupled to the internal light guide, which is typicallyalso a fiber optic bundle. Typically, the external source and theinternal optical fiber light guide are standard parts that arecommercially available. The coupling efficiency, that is, the amount oflight that actually passes from the light source to the viewing area, isrelatively poor.

The poor coupling efficiency results in part from the difficulty incontrolling the light emitted from the external source fiber opticbundle and focusing that light into the internal light guide and in partfrom the physical structure of a bundle of optical fibers. Matching thenumerical aperture and spot size of the external source in the receivinginternal light guide is very important for coupling efficiency. Thenumerical aperture of an optical fiber is a mathematical representation(the sine of the half angle of the full cone of light that can beaccepted by the optical fiber and completely transmitted without anyloss) of the angle at which light may strike the surface of an opticalfiber that is perpendicular to the optical axis of the fiber and stilltravel down the fiber. Light that strikes that surface at too great anangle as measured from the optical axis of the fiber, i.e. exceeds thenumerical aperture of the fiber, will be lost. The spot size of a lightbeam is defined by the circular area within which a large percentage ofthe light is contained at a particular distance from the source of thelight beam. The most efficient light transfer occurs when thetransmitted light falls within the numerical aperture of the receivingfibers and the spot size of the transmitted light is smaller than thecore of the receiving fiber. A focusing lens or focusing system may beused to aid in directing the light from the source appropriately.Typically, if the spot size of the external light source is reduced by afocusing lens, then the cone angle of the converging light from thefocusing lens may exceed the numerical aperture of the receiving fiber,and the light that exceeds the numerical aperture of the receiving fiberwill be lost. Conversely, if the cone angle of the converging light isless than the numerical aperture of the receiving fiber, then the spotsize of the converging light may be larger than the core size of thereceiving fiber, and the light that exceeds the core size of thereceiving fiber will be lost. Matching the numerical aperture and spotsize of the source fiber to those of a receiving fiber, such as betweenthe external light source and the internal light guide, can beespecially difficult when the source is a bundle of fibers. Also, whenattempting to focus light from a bundle of fibers into a second bundleof fibers, the coupling efficiency is greatly reduced because a singlefocusing system is attempting to focus a group of spots simultaneously.Since only one ray is actually on the focusing system opticalcenterline, all other rays from the source fibers, as they spread outfrom the center of each fiber, are decentered and unsymmetrical in thefocusing lens. They therefore cannot match both the spot size andnumerical aperture of the receiving fibers. The greatest couplingefficiency is achieved through a compromise between the spot size andthe cone angle of the converging light, i.e., when the converging lightmost nearly matches the core size and numerical aperture of thereceiving fiber and when the optical centerlines of the emitting fiber,the focusing system, and the receiving fiber are coaxial.

An additional problem that leads to poor light transmission to theviewing area results from the construction of bundles of fibers. Asingle optical fiber consists of a core (the light carrying portion) andthe cladding (the covering of the core that causes the light to staycontained within the core). Only the cores of the bundled fibers carrylight; therefore, light is lost due to the spaces between the cores.When a group of fibers having circular cross-sections is bundled into acylindrical configuration, only about 78% of the cross-sectional area ofthe cylindrical configuration is taken up by fibers. Also, the core ofeach of the bundled fibers is smaller than the cladding. Consequently,the actual light-carrying area is significantly smaller than thecircular cross-section of the bundle. Improved light transmission to thedistal end of the arthroscope will improve the illumination of theviewing area and increase the information contained in captured images.

There is a need for an arthroscope that affords a wide effective fieldof view and that does not require movement of the arthroscope to varyits scope of view. One such arthroscope is disclosed in copending U.S.application Ser. No. 09/243,845, entitled “Variable View Arthroscope;”which has a common inventor with the present application. Another sucharthroscope is disclosed in copending U.S. application Ser. No.09/452,340, entitled “Variable View Arthroscope;” which also has acommon inventor with the present application. The referencedapplications are incorporated herein by this reference. There is also aneed for an improved light relay system for illuminating the viewingarea through an arthroscope. In this specification and in the appendedclaims the term “arthroscopd” means and should be interpreted to includean endoscope or any other similar optical instrument, whether used forsurgery or otherwise.

SUMMARY OF THE INVENTION

A variable view arthroscope in accordance with the present inventionincludes a variable object input assembly in an elongated housing tube,a control to vary the view of the object input assembly, and a lightingassembly to illuminate the viewing area. An input window, located in theinput end of the housing tube, allows a view of the working area. Theinput window is preferably spherical. The object input assembly includesan input lens, a first mirror, and a second mirror. The input lens ismovable and the first mirror is rotatable. The input lens and the firstmirror move around the same axle. The second mirror is fixed. Thereflected light from the viewing area forms a working image and thelight image or object rays pass from the viewing area through the inputwindow and the input lens, reflect from the first mirror to the secondmirror, and reflect from the second mirror into a relay lens system. Insome embodiments, the second mirror may be replaced by a prism.

The control varies the position of the input lens and first mirror toany position, or to a series of fixed positions, between a first limitposition and a second limit position. As object rays pass through theinput lens to the first mirror, to the second mirror or prism, and intothe relay lens system, the length of the axial ray remains the same whenthe angle of view of the arthroscope changes. Also, the lengths of therim rays may be equal to each other and may also remain the same whenthe angle of view of the arthroscope changes.

In another aspect of the invention, the lighting assembly preferablyincludes a relay light guide formed from one or more rods of transparentmaterial with mirrored surfaces. The relay light guide preferablycaptures each light ray from an external source and transmits the ray tothe viewing area.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the present invention, reference should bemade to the following detailed description taken in connection with theaccompanying drawings, not drawn to scale, in which the same referencenumerals indicate the same or similar parts, wherein:

FIG. 1 is a plan view of a variable view arthroscope in accordance withan embodiment of the present invention;

FIG. 2 is a sectional elevation view of the variable view arthroscope ofFIG. 1;

FIG. 3 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, showing portions of an object input assembly inaccordance with an embodiment of the present invention, adjusted for amaximum upward view;

FIG. 4 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, showing portions of an object input assembly,adjusted for a maximum downward view;

FIG. 5 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, showing superimposed the portions of an objectinput assembly for the arthroscope adjusted for both a maximum upwardview and a maximum downward view;

FIG. 6 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, adjusted for an intermediate view, furthershowing an input lens control in accordance with an embodiment of thepresent invention.

FIG. 7 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, adjusted for an intermediate view, furthershowing a first mirror control, in accordance an embodiment of thepresent invention;

FIG. 8 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, adjusted for an intermnediate view, showing bothan input lens control and a first mirror control, in accordance with anembodiment of the present invention;

FIG. 9 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, adjusted for a maximum upward view, showing bothan input lens control and a first mirror control, in accordance with anembodiment of the present invention;

FIG. 10 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, adjusted for a maximum downward view, showingboth an input lens control and a first mirror control, in accordancewith an embodiment of the present invention;

FIG. 11 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, showing portions of an object input assembly, inaccordance with another embodiment of the present invention, adjustedfor an intermediate view;

FIG. 12 is a sectional elevation view of the object input end of thearthroscope of FIG. 1, showing the portions of an object input assemblyand related controls, in accordance with an embodiment of the presentinvention, adjusted for an intermediate view.

FIG. 13 is a sectional elevation view of a lighting system for anarthroscope in accordance with an embodiment of the present invention.

FIG. 14 is a sectional elevation view of the lighting system of FIG. 13,further showing the transmission of light rays through the system.

FIG. 15A is an elevation view of a slide portion of an arthroscopecontrol in accordance with an embodiment of the present invention.

FIG. 15B is a plan view of the slide of FIG. 15A.

FIG. 15C is an end view of the slide of FIG. 15A.

FIG. 16A is a plan view of a can/axle member of an arthroscope controlin accordance with an embodiment of the present invention.

FIG. 16B is an end view of the cam/axle member of FIG. 16A.

FIG. 16C is an elevation view of the cam/axle member of FIG. 16A.

FIG. 17A is a plan view of two control knobs of an arthroscope controlin accordance with an embodiment of the present invention.

FIG. 17B is an end view of the control knobs of FIG. 17A.

FIG. 17C is a sectional view, along line 17c—17c in FIG. 17A, of thecontrol knobs.

FIG. 18A is a plan view of the slide and cam/axle relationship in thecenter travel position in accordance with an embodiment of the presentinvention.

FIG. 18B is a sectional view along line 18B-D in FIG. 18A showing theslide and cam/axle relationship in the center travel position inaccordance with an embodiment of the present invention.

FIG. 18C is a sectional view along line 18B-D in FIG. 18 A showing theslide and cam/axle relationship in the full aft travel position inaccordance with an embodiment of the present invention.

FIG. 18D is a sectional view along line 18B-D in FIG. 18A showing theslide and cam/axle relationship in the full forward travel position inaccordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A variable view arthroscope in accordance with an embodiment of thepresent invention is shown in FIGS. 1 and 2. Although shown anddescribed herein as an arthroscope providing up-down view variability, asimilar configuration could be oriented so as to provide side-to-sideview variability or view variability along any other axis. A variableview arthroscope, generally indicated at 30, includes an elongatedhousing tube 31, with an object input end 32 and a control end 33, thatextends along a central, longitudinal axis. Arthroscope 30 includes anouter control portion 35. Housing tube 31, and more specifically itscontrol end 33, may extend into the outer control portion 35 ofarthroscope 30. Generally, an image object is captured at the objectinput end 32 of housing tube 31, relayed to the control end 33, andrecorded and displayed from the outer control portion 35 of arthroscope30. As discussed herein, the image object is formed of object rays andthe object rays include an axial ray at the optical center of the objectimage, and rim rays at the outer edges or rims of the object image.

The control portion 35 ends with a CCD attachment 36. The CCD attachment36 is connected by appropriate means to an image screen (not shown) tobe viewed by a person using arthroscope 30. CCD attachment 36 may be ofconventional construction and is not shown in detail. The outer controlportion 35 may also include a control, such as a slide, for adjustingthe view of the arthroscope 30, and a focusing lens assembly 55 foradjusting the focus of the arthroscope 30. The focusing lens assembly 55may include a focusing lens, a zoom lens, and their controls. Thefocusing lens assembly directs the object received from the input end 32into the CCD attachment 36. At the outer control portion 35, thearthroscope includes a portion of a lighting assembly 42, formed from alight source 41 that is connected to a light relay assembly 43. Thelighting assembly 42 illuminates a viewing area beyond the object inputend 32 of the housing tube 31. The viewing area is preferably an area infront of the object input end 32 of the arthroscope, from about 15degrees below the longitudinal axis of the arthroscope tube 31 to about105 degrees above the longitudinal axis of the arthroscope tube 31.

Referring now to FIGS. 3-5, the object input end 32 includes an objectinput assembly 50. In preferred embodiments, the object input assembly50 includes an input window 52, an input lens 54, a first mirror 56 anda second mirror 58. In obtaining an image of the object, the object rayspass from the viewing area into the input window 52 and through theinput lens 54, and are reflected from the first mirror 56 to the secondmirror 58.

The input end 32 of housing tube 31 is preferably beveled and closed byinput window 52. The input window 52 is preferably a concentricspherical meniscus lens and formed so that the curvatures of the outerand inner surfaces are concentric to each other around a commoncenterpoint. Preferably, the centerpoint is on the centerline of theaxle 90, which is on the front reflecting surface of the first mirror 56(as discussed further below). Also, preferably, the centerpoint is onthe optical axis of the input lens 54. If the centerpoint of the inputwindow 52 is positioned on the input lens optical axis, a constantrelationship is maintained between the refractive angles of the inputobject rays as the input lens 54 moves from position to position. As aresult, the refraction of the input object rays through the input window52 is constant with respect to the input lens 54 and distortions arereduced. The dimensions of the input window 52 preferably are selectedto maximize the range of view of the arthroscope 30 in cooperation withthe other elements of the object input assembly. Input window 52 may beformed of glass or some other suitable material. The input window 52 isfixed in place, such as by adhesive, and also may be sealed to form asealed closure for the end of the housing tube 31. Preferably, input end32 of housing tube 31 is formed so that the edges of the housing tube 31have a shape similar to the profile shape of the input window 52 andextend beyond the surface of input window 52 to afford the greatestprotection to the input window 52 without interfering with the inputobject rays during operation of the arthroscope 30.

The input lens 54 and the first mirror 56 are movable and together varythe view of the arthroscope 30 and direct the captured image to thesecond mirror 58. The common axle around which both the input lens 54and the first mirror 56 move and, with respect to which they arepositioned, defines a preferred alignment of the input lens 54 and thefirst mirror 56. The input lens 54 of the object input assembly 50 ispositioned inside the input end 32 of housing tube 31 proximate to theinput window 52. In the embodiments illustrated in FIGS. 3-10, inputlens 54 is a conic negative lens. However, any suitable lens may beused. The input lens 54 is movable and rotates around the axle 90. Theinput lens 54 rotates between a maximum upward view position (FIG. 3)and a maximum downward view position (FIG. 4), approximatelycorresponding to and limited by the field of view afforded by the inputwindow 52. The input lens 54 is preferably fixedly mounted on an inputlens frame 80. The input lens frame 80 supports the input lens 54 at oneend and pivots around the axle 90 at the other end. The input lens frame80 is moved by a control mechanism. The input lens 54 is mounted on theinput lens frame 80 so that the optical centerline or axis of the inputlens 54 is directed to the centerline of the axle 90.

The first mirror 56 is accordingly positioned to reflect the object raysreceived from the input lens 54 to the second mirror 58, which is fixed.The first mirror 56 pivots around the axle 90, in a motion complementaryto that of the input lens 54. The centerline of the axle 90 is coplanarwith the front reflecting surface of the first mirror 56. As the inputlens 54 moves, the position of the first mirror must change to preservethe desired orientation of the object rays. Due to the geometry ofmirrors, the angle change in a ray reflected from a mirror will bedouble rid the angle change in the reflecting plane of the mirror, suchas when the mirror rotates from a first position to a second position.Consequently, the first mirror 56 rotates around the axle 90 at half therate of angular change at which the input lens 54 rotates around theaxle 90, in a complementary direction. That is, as the input lensrotates around the axle 90 through a first angle of rotation, the firstmirror 56 pivots around the axle 90 through a second angle of rotationthat is half the first angle of rotation. The first mirror 56correspondingly rotates between a maximum upward view position (FIG. 3)and a maximum downward view position (FIG. 4). Together with themovement of the input lens 54, the rotation of the first mirror 56varies the view of the arthroscope 30. In alternative embodiments, theinput lens 54 and the first mirror 56 may be moved between a series ofpre-defined positions or may be moved to any position within the rangeof the arthroscope 30. The first mirror 56 is preferably mounted on afirst mirror frame 86. A control adjusts the position of the firstmirror 56. In the middle view of the object input assembly 50, thereflecting surface of the first mirror 56 is horizontal with respect tothe longitudinal orientation of tube 3 land the input lens 54 ispositioned so the optical axis of lens 54 is at an angle 45 degrees upfrom the plane of mirror 56. In the illustrated embodiment, the centerof the middle view is therefore 45 degrees up from the horizontal (FIG.6), i.e., the longitudinal axis of the tube 31.

The object rays obtained through the input lens 54, first mirror 56, andsecond mirror 58 are preferably relayed to the outer control portion 35of the arthroscope 30 via the relay lens assembly 60. It is preferredthat the rays be relayed so as to preserve the quality of the image andto minimize aberrations. The second mirror 58 is fixed in position toreflect the captured object rays into the relay lens assembly 60. Thesecond mirror 58 is preferably aligned to orient the reflected objectrays parallel to the optical axis of the relay lens assembly 60, whichaxis is preferably parallel to the longitudinal axis of the housing tube31. The relay lens assembly 60 is preferably coaxial with the axial rayreflected from the second mirror 58. In various embodiments, the relaylens assembly 60 is a lens or a series of lenses, one alternative ofwhich is commonly referred to as a field and relay lens system. Inadditional embodiments, the relay lens assembly 60 may be a graded indexlens or other lens having a varying refractive index. In alternativeembodiments, the relay lens assembly 60 may be replaced by an opticalfiber coherent bundle. Although the relay lens assembly 60 is shown asbeing contained within the input end 32 of the housing tube 31, therelay lens assembly 60 typically extends further towards the control end33. If the relay lens assembly 60 is replaced with a coherent bundle ofoptical fibers or is replaced with a graded index lens system, each willtypically extend substantially along the length of housing tube 31. Therelay lens assembly 60 may be of conventional construction, e.g., havingan outer stainless steel sleeve for stability, or the relay lensassembly 60 may rest in a groove cut into relay light guide 120. Therelay lens assembly 60 directs the object rays toward a receptor, suchas a focusing lens assembly 55.

The movement of the input lens 54 and the first mirror 56 allows theviewing position of the arthroscope 30 and thus the particular inputimage captured in the arthroscope 30 to be variable. The control thatadjusts the input lens 54 and the first mirror 56 adjusts themcongruently to maintain the desired alignment. Referring to FIGS. 6-10,preferably, a push rod 70 directs the motion of the input lens 54 andthe first mirror 56. The position of the input lens 54 is adjusted bythe push rod 70 engaging the input lens frame 80 through an input lensconnecting rod 74. The input lens connecting rod 74 is connected to thepush rod 70 at push rod yoke 72 by yoke pin 76. The input lensconnecting rod 74 is connected to the input lens frame 80 through aninput lens frame pin 78. As the push rod 70 moves back and forth alongthe longitudinal axis of the housing tube 31, the connecting rod 74shifts the position of the input lens frame 80 and, hence, of the inputlens 54. The position of the first mirror 56 is adjusted by the push rod70 engaging the first mirror frame 86 through a first mirror connectingrod 82. The first mirror connecting rod 82 is connected to the push rod70 at push rod yoke 72 by yoke pin 77. Yoke pins 76 and 77 are disposedon opposite sides of the push rod yoke 72 and are coaxial. The firstmirror connecting rod 82 is connected to the first mirror frame 86through a first mirror frame pin 84. As the push rod 70 moves back andforth, the first mirror connecting rod 82 adjusts the angle of the firstmirror 56.

The first mirror connecting rod 82 is fastened to the push rod yoke 72at yoke pin 77 and the input lens connecting rod 74 is connected to theyoke at yoke pin 76. Because yoke pins 77 and 76 are coaxial, bothconnecting rods move synchronously. Preferably, the distance from theaxle 90 to the input lens frame pin 78 is one half the distance from theaxle 90 to the first mirror frame pin 84. As the push rod 70 moveslaterally a certain distance, the angular change of the input lens 54 ispreferably twice the angular change of the first mirror 56 since theradius of the input lens arc is one half the radius of the first mirrorarc. The illustrated positioning and relative proportions of theconnecting rods, axle and input lens frame pin and first mirror framepin in FIGS. 8-10 preferably minimize any error in the relative angularchanges. It should be understood that any mechanical arrangement thatpreserves the desired geometries of the mirrors and the input lens issuitable; for example, more than one push rod may be effective.

To minimize distortion in the recorded image, preferably, the object raypath lengths remain constant as the view of the arthroscope varies. Theobject axial ray 62 passes through the optical center of the input lens54 to the center of the first mirror 56. This distance is fixed becausethe center of the first mirror 56 is fixed on the centerline of the axle90 around which the input lens 54 rotates with a constant radius. Theobject axial ray 62 then reflects from the center of the first mirror 56to the second mirror 58, which is fixed with respect to the first mirror56. The axial ray then reflects from the second mirror 58 along theoptical axis of the relay lens assembly 60, which is fixed with respectto second mirror 58. Because each segment of the object axial ray 62 hasa fixed length, the length of the object axial ray 62 from the inputlens 54 to the relay lens system 60 remains constant as the view of thearthroscope 30 varies. The object rim rays 64 pass through the inputlens 54 to the first mirror 56. Because axial ray 62 is coaxial with theoptical axis of input lens 52, all object rim rays 64 are symmetricabout axial ray 62. As long as all object rays are reflected orrefracted symmetrically to any plane normal to axial ray 62, such as thefirst lens of the relay lens system 60, the length of the object raysremain constant. In some embodiments of the present invention, thisfeature may allow the view to change without changes in distortion andimage quality.

Referring now to FIGS. 11 and 12, in an alternative embodiment, ratherthan second mirror 58, a fixed prism 59 may orient the image raysreflected from the first mirror 56 into the relay lens assembly 60. Theprism 59 receives object rays and internally reflects them in thedesired direction. Because the input and output surfaces of prism 59 arenormal to the object axial ray 62, and the object rim rays 64 are almostparallel at this point, the prism 59 preserves relative ray lengthssimilar to second mirror 58. Replacing second mirror 58 with prism 59reduces the input lens system focal length, thereby improving imagequality. Also, as illustrated in FIGS. 11 and 12, the input lens 54 maybe a doublet consisting of two spherical lenses, which may be easier toconstruct than a single conic negative lens of very small size.

The lighting assembly 42, illustrated in FIG. 2, includes a light source41 with an external optical fiber light guide to transmit light to thelight relay assembly 43 that extends into the arthroscope 30. Anyconventional external light source and light guide may be used.Typically, the external light source 41 is connected at an angle obliqueto the axis of the housing tube 31. The lighting assembly 42 may includea condenser lens to focus light from the external source 41 onto theinput end of the light relay assembly 43. The light relay assembly 43reorients the light along the longitudinal axis of the housing tube 31and transmits the light to the end 32 of the housing tube 31. The lightrelay assembly 43 may include one or more optical fiber bundles. In someembodiments, the light relay assembly 43 is an optical fiber bundle thatextends to the input end 32 of the arthroscope 30. In alternativeembodiments, the light relay assembly 43 may include structures otherthan optical fiber bundles. Referring to FIGS. 13 and 14, in sameembodiments, the light relay assembly 43 is a rod-based light relayassembly 100, including an input rod 110 and a relay rod 120. Oneadvantage of some embodiments of rod-based light relay assembly 100 isthat the cross-section is defined by only one rod and light is not lostas between the cores of fibers in a fiber optic bundle. The rods 110 and120 are preferably joined to each other so that the input light guiderod 110 receives the light from the optical fiber light guide of theexternal light source 41and transmits it to the relay rod 120. The relayrod 120 transmits the light from the input rod 110 to the distal end 32of the arthroscope 30 to light the viewing area. The light relayassembly 100 is preferably designed to transmit the maximum amount oflight from the light source to the viewing area. The light relayassembly 100 preferably is designed to accommodate light that is skewedwith respect to the optical axis of the light relay assembly; the lightmay typically be skewed by 40 degrees or more from the optical axis.Each of the optical fibers of the external light guide of the externallight source 41 emits a cone of light equal to twice the numericalaperture of the fiber. At the edge of each cone are the maximum skewrays and at the center of each cone is the central ray. In between themaximum skew rays, an infinite number of rays fans out from the centralray. Preferably every ray is transmitted to the viewing area. FIG. 14illustrates the path of both a central ray 130 and skew rays 132 thatare transferred through the light relay assembly 110.

The input rod 110 and the relay rod 120 are formed from plastic or othertransparent material, such as acrylic or polycarbonate, that is suitableto act as a light guide. The relay rod is preferably positioned so thatit extends at an angle to the input rod, for example so that it isperpendicular, to accommodate the orientation of the external lightsource 41 with respect to the housing tube 31 and redirect the lightalong the axis of the tube 31. Light from the external source 41 entersthe input rod 110, turns where the input rod 110 joins the relay rod120, and passes out the opposite end of the relay rod 120 through theinput window 52 to the viewing area. Both the input rod 110 and therelay rod 120 have entirely mirrored surfaces except for the input endand the output end of each. Because of the mirrored surfaces, lightrelay assembly 100 does not depend on the numerical aperture limits oftotal internal reflection to gather and transmit light through itslength. As a result, mismatched spot sizes, optical fiber corelocations, and mismatched numerical apertures do not cause loss oflight-gathering and transmission efficiency as often occurs in opticalfibers. Preferably, every ray entering the input rod 110 is reflectedinto the relay rod 120 at the joint between the input rod 110 and therelay rod 120 and through the relay rod 120 to the viewing area.

The input rod 110 is mirrored on its surface except at its input face111 and output face 112. Preferably, the diameter of the input rod 110is equal to or slightly larger than the overall diameter of the externallight guide. Preferably, the diameter of the relay rod 120 is largerthen the diameter of the input rod 110. With the rods 110, 120positioned at a 90 degree or other angle from one another, a largerdifference in the diameter of the rods 110, 120 will improve theefficiency of the turning of the light. The diameter of relay rod 120 isdetermined by the available space inside tube 31. The curve 121 ispreferably dimensioned to ensure that the maximum skew ray is reflecteddown the length of relay rod 120 and not back through input rod 110. Theangle of the maximum skew ray depends on the light that is emitted fromthe external source 41. The input end of the relay rod 120 is curved atthe surface 121 where light entering from the input rod reflects, i.e.,the surface 121 opposite the surface where the relay rod 120 is joinedto the input rod. Preferably, the radius of the curve 121 issubstantially equal to or larger than the diameter of the relay rod 120.Preferably, referring to the illustrations in FIGS. 13, the center 124of the curve 121 is to the left of the left edge of the input rod 110.

The relay rod 120 preferably extends along the longitudinal axis of thehousing tube 31 and ends near the input window 52 of the arthroscope 30.The relay rod 120 is mirrored on its surface except where it receiveslight from the input rod 110 on face 112 and where it releases light atsurface 123. The output end of the relay rod 120, proximate to the inputwindow 52, has an upper curved portion 123 and a lower curved portion122. The lower curved portion 122 is mirrored to reflect light in thedesired direction, i.e., out the input window 52. The upper curvedportion 123 is clear to allow the transmitted light to escape throughthe end of the rod 120 through the window 52 to illuminate the viewingarea. Preferably, together the lower curved portion 122 that is mirroredand the upper curved portion 123 that is clear provide as much light aspossible to the viewing area and reduce diffusion of light intonon-working areas that need not be illuminated. The location of thecenter of the lower curved surface 122 and length of the lower curvedsurface 122 determine the angle from which the viewing area will belighted and the amount of light directed to the working area. The radiusof the lower mirrored curved surface 122 is preferably equal to orlarger than the diameter of the relay rod 120. Referring to theillustration in FIGS. 13, the center 125 of the lower curve 122 is tothe left of the end of the mirrored surface on the upper portion of therelay rod end. Preferably, every light ray will be reflected forwardtoward the viewing area by surface 122 and not back through the relayrod 120. The proportions of the upper curved surface 123 also determinethe amount of light and direction of the light rays leaving the relayrod 120. The upper curved surface 123 is preferably designed so thatlight rays reflecting from the lower curved surface 122 strike the uppercurved surface 123 at less than the critical angle of upper curvedsurface 123, and escape rod 120, rather than internally reflecting backthrough the rod 120. The upper curved surface 123 preferably diffusesthe light with an even distribution across the viewing area. The exactproportions of the upper and lower surfaces 122, 123 will depend on thedesired illumination properties of the arthroscope 30 for the viewingarea.

FIGS. 15A-18D illustrate a mechanism for manipulating the push rod tooperate the object input assembly control and adjust the view of thearthroscope 30. At the control end 35 of the arthroscope 30 the push rod70 extends into and engages a slide 148. The slide includes a main body157 having an axial relay lens opening 158; the relay lens opening 158also extends through an enlarged end 159 of the slide 148. A socket 161aligns and attaches push rod 70 to slide 148. In the illustratedembodiment, the control rod socket 161 is located directly below theaxial opening 158 for the relay lens.

The cam portion 165 of cam/axle member 162 is positioned in a centraltransverse opening 163 in slide 148. Opening 163 is not quite circularin cross-section; it is enlarged or stretched slightly. The cam/axlemember 162 includes a large control knob shaft attachment segment 164 ofcircular cross-section; a circular off-axis cam segment 165 contains arelay lens assembly slot 166, and a small control knob shaft attachmentsegment 167. Two control knobs, 149, 150 shown in FIGS. 17A-17C, aremounted on the outer ends 164 and 167 of cam/axle member 162. Thecontrol knobs 149, 150 include a righthand control knob 149 that isfitted onto the large control wheel shaft attachment segment 164 of thecam/axle member 162. The second or lefthand control knob 150 fits ontothe smaller control knob shaft attachment segment 167 of cam/axle member162. Rotation of the control knobs 149, 150 that are attached tocam/axle 162 cause the off-axis cam 165 of cam/axle 162 to engage thecentral transverse opening 163 of slide 148, causing slide 148 to movelaterally, as indicated by dashed areas 168 in FIGS. 18C and 18D, inresponse to the rotary motion of cam/axle 162.

In alternative embodiments, the slide 148 may also be electricallydriven. Slide 148 may be driven by a step motor. A step motor may drivecam/axle 162, or cam/axle 162 may be replaced with, for example, a jackscrew engaging slide 148. The step motor and jack screw are preferablyinternal to the arthroscope 30 and mounted parallel to the motion ofslide 148. Slide 148 may also be driven with a piezoelectric positionermounted internally to the arthroscope 30. The arthroscope 30 may beelectrically operable by electrical buttons or by operating software ona computer, for example.

Operation of the arthroscope 30 can now be considered. At the outset,light from external source 41 is focused upon the end of the light relayassembly 43, which is preferably a rodbased light relay assembly 100.Light passes through the light relay assembly 43 and illuminates asurgical working area just beyond the input end 32 of the arthroscope30. In arthroscope 30, light passing through light relay assembly 43 mayreflect, at least in part, from the second mirror 58 onto the reflectivesurface of the first mirror 56, and then pass through the input lens 54into the viewing area to be illuminated. Light reflected from theviewing area passes through input window 50 and input lens 54 as objectrays which impinge on first mirror 56. The object rays are directed fromthe first mirror 56 to impinge upon the second mirror 58 or prism 59.From the second mirror 58 or prism 59 the object rays are re-directedtoward the input end of the relay lens assembly 60. The relay lensassembly 60 supplies the image to the CCD attachment 36, throughfocusing lens assembly 55, to be viewed by the surgeon or other personusing the arthroscope 30.

If the person using arthroscope 30 is dissatisfied with the imageavailable through the CCD attachment 36, control knobs 149, 150 may beused to provide an image of a different portion of the surgical region.In this way the image supplied to the surgeon or other person using theinstrument 30 can be and is varied to a substantial extent with nochange in the position of the instrument. In effect, the overall viewingrange of the instrument 30 may extend from about 15 degrees below thelongitudinal axis of the housing tube to about 105 degrees above theaxis of the housing tube, with no need to change the axis of theinstrument. Further alteration or correction of the image may beeffected by appropriate software.

Several parts of instrument 30 can be modified from those illustratedwithout appreciable effect on overall operation of instrument 30. Forexample, the push rod 70 may be modified; the push rod 70 constitutes anoptional mechanism for operating the input lens and first mirror but anymechanism that will move the input lens and first mirror in therelationship described can be used. The cam/axle and slide controlmechanism may also be altered. The angle of the bevel of the outer endof housing tube 31 may be varied as desired; a curved shaped similar tothe profile shape of the input window and extending beyond the inputwindow so as to provide maximum protection to the input window withoutinterfering with the object rays is preferred, but may depend on theprimary use for instrument 30. It will be recognized that use of a CCDunit for a display is not essential. The software used for the displaymay vary appreciably.

The language used herein is used for purposes of reference and notlimitation. While the invention has been particularly shown anddescribed with reference to preferred embodiments, it will be apparentto those skilled in the art that various modifications and alterationscan be made in the device of the present invention without departingfrom the spirit and scope of the invention.

What is claimed is:
 1. A variable view arthroscope having more than oneviewing position, including a first viewing position and a secondviewing position, comprising: an input lens rotatable around a commonaxis; a first mirror rotatable around the common axis, the common axisbeing coplanar with a reflecting surface of the mirror; an object relayassembly; wherein, the input lens, the first mirror and the object relayassembly are arranged so that object rays pass through the input lens tothe first mirror and reflect from the first mirror toward the objectrelay assembly, and wherein the angular rotation of the first mirroraround the common axis between the first viewing position and the secondviewing position is half the angular rotation of the input lens aroundthe common axis between the first viewing position and the secondviewing position.
 2. The variable view arthroscope of claim 1, furthercomprising a fixed aligning optical element, the fixed aligning opticalelement being positioned so that object rays reflect from the firstmirror to the aligning optical element and from the aligning opticalelement into the object relay assembly.
 3. The variable view arthroscopeof claim 2, further comprising a housing tube enclosing the input lens,the first mirror, the aligning optical element and the object relayassembly, the housing tube having a viewing end, the viewing end beingclosed by an input window, the input window being spherical and having afirst surface with a curvature and a second surface with a curvature,the curvatures of the first and second surfaces of the input windowbeing concentric around a common centerpoint.
 4. The variable viewarthroscope of claim 2, wherein the aligning optical element is a secondmirror.
 5. The variable view arthroscope of claim 2, wherein thealigning optical element is a prism.
 6. The variable view arthroscope ofclaim 2, wherein the input lens is a conic negative lens.
 7. Thevariable view arthroscope of claim 2, wherein the input lens is adoublet of two spherical lenses.
 8. The variable view arthroscope ofclaim 1, further comprising a housing tube enclosing the input lens, thefirst mirror, the aligning optical element and the object relayassembly, the housing tube having a viewing end, the viewing end beingclosed by an input window, the input window being spherical and having afirst surface with a curvature and a second surface with a curvature,the curvatures of the first and second surfaces of the input windowbeing concentric around a common centerpoint.
 9. The variable viewarthroscope of claim 8, wherein the common centerpoint is on the commonaxis.
 10. The variable view arthroscope of claim 1, further comprisingan input lens frame, wherein the input lens is mounted on a first end ofthe input lens frame, the input lens frame having a second end proximateto the common axis and having a pivot point at the common axis.
 11. Thevariable view arthroscope of claim 10, further comprising a control, thecontrol including a push rod having a slide end and an input assemblyend.
 12. The variable view arthroscope of claim 11, the control furtherincluding a push rod yoke attached to the push rod at the input assemblyend, an input lens connecting rod attached to the push rod yoke by afirst yoke pin and to the input lens frame by an input lens frame pin,the first mirror being mounted on a first mirror frame, and a firstmirror connecting rod attached to the push rod yoke by a second yoke pinand to the first mirror frame by a first mirror frame pin, the first andsecond yoke pins being coaxial.
 13. The variable view arthroscope ofclaim 12, wherein the distance from the common axis to the input lensframe pin is half the distance from the common axis to the first mirrorframe pin.
 14. The variable view arthroscope of claim 11, the controlfurther including a slide attached to the push rod at the slide end, theslide being longitudinally movable, a cam-axle assembly for moving theslide, and a view control to manipulate the cam-axle assembly.
 15. Thevariable view arthroscope of claim 1, wherein the optical axis of theobject rays intersects the common axis in the first viewing position andin the second viewing position.
 16. The variable view arthroscope ofclaim 1, further comprising a first mirror frame, wherein the firstmirror is mounted on the first mirror frame, the first mirror framehaving a pivot point at the common axis.
 17. A variable viewarthroscope, comprising: an input lens which is rotatable; a firstmirror which is rotatable; and an object relay assembly; wherein theinput lens, first mirror and object relay assembly are arranged tocooperate to capture and direct object rays so that the rays passthrough the input lens to the first mirror, and reflect from the firstmirror towards the object relay assembly, rotation of the input lensvarying the view of the arthroscope, and wherein the angle of rotationof the first mirror is coordinated to be half the angle of rotation ofthe input lens.
 18. The variable view arthroscope of claim 7, whereinthe input lens and the first mirror are rotatable around a common axisand the common axis is coplanar with a reflecting surface of the firstmirrors .
 19. The optical system of claim 17, further comprising asecond mirror, wherein the first mirror reflects object rays to thesecond mirror and the second mirror directs object rays to the objectrelay assembly.
 20. The variable view arthroscope of claim 19, whereinthe second mirror fixed.
 21. The variable view arthroscope of claim 18,wherein the optical axis of the object rays intersects the common axisas the view of the arthroscope is varied.
 22. The variable viewarthroscope of claim 17, further comprising wherein the object relayassembly is a relay lens system, further comprising a prism, wherein thefirst mirror reflects object rays to the prism and the prism directsobject rays into said relay lens system.
 23. The variable viewarthroscope of claim 22, the relay lens system having an optical center,wherein the prism is fixed and is oriented to reflect an axial objectray received from the first mirror to the optical center of the relaylens system.
 24. The variable view arthroscope of claim 17, wherein theinput lens and the first mirror are rotatable around a common axis andthe common axis is transverse to the optical axis.